In perfect bookbinding machines, EVA (Ethylene Vinyl Acetate) hot-melt adhesive (referred to as “EVA adhesive” hereinafter) is generally used. The EVA adhesive can be easily treated because it infinitely repeats the cycle of melting by heating and hardening by cooling on the one hand, and has a defect of unsatisfied adhesion force on the other hand.
Hence PUR (Poly Urethane Reactive) hot-melt adhesive (referred to as “PUR adhesive” hereinafter), whose adhesion force is much stronger than that of the EVA adhesive, has attracted attention in recent years. The PUR adhesive has a characteristic that it hardens by reacting with water contained in air or paper and never softens even when heated if once it hardens.
Accordingly, in a bookbinding machine using the PUR adhesive, an adhesive application mechanism suitable for the characteristic of the PUR adhesive is required.
That is to say, in the case of manufacturing the same product in large quantities, just like a bookbinding machine using the EVA adhesive, a roller type adhesive application mechanism is provided and the PUR adhesive is applied to a spine of a book block by one or more adhesive application rollers while a clamper by which the book block is gripped in a standing state passes over the roller type adhesive application mechanism.
On the other hand, in the case of manufacturing a wide variety of products in small quantities, a nozzle type adhesive application mechanism rather than the roller type adhesive application mechanism is provided and the PUR adhesive is applied by spraying the PUR adhesive from a spray nozzle to a spine of a book block (see, for example, Patent Document 1).
The nozzle type adhesive application mechanism comprises a spray nozzle directed toward a path of conveying a book block, an adhesive supply source, an adhesive supply pipe for supplying the adhesive from the adhesive supply source to the spray nozzle, and a pump connected to the adhesive supply pipe. By using this adhesive application mechanism, the adhesive is sprayed from the spray nozzle and applied to a spine of the book block while a book block gripped by a clamper is conveyed along a conveying path.
Incidentally, because the amount of adhesive to be applied to a book block's spine changes depending on the thickness of the book block, the nozzle type adhesive application mechanism requires changing a rotational speed of the pump to control the amount of adhesive fed into the spray nozzle. In this case, the thickness of adhesive applied to the book block's spine changes depending on change of a conveying speed of the clamper even if the amount of adhesive fed into the spray nozzle is the same.
Accordingly, taking not only the thickness of the book block but also the conveying speed of the clamper into consideration, the rotational speed of the pump should be controlled.
Also, because sheets or signatures making up the respective book blocks have different qualities and thicknesses and different kinds of adhesive have different characteristics, the thickness of adhesive to be applied to the book block's spine should be determined taking not only the thickness of the book block but also those conditions into consideration.
Furthermore, because an appearance of a product (book) is subjectively evaluated and a criteria of the evaluation varies for each of users, it may be desired by the users to set the thickness of adhesive to be applied to the book block's spine in a manner such that products suitable for tastes of the users can be obtained.
Hence, the users conduct test operations of the bookbinding machine, makeup a table of rotational speed values of the pump of the nozzle type adhesive application mechanism based on results of the test operations and perform initial setting of the rotational speed of the pump by using the table prior to an operation of the bookbinding machine.
However, the preparation of this table is achieved by bookbinding actually while changing combinations of the thickness of the book block, the rotational speed of the pump and the conveying speed of the clamper and so on in various ways, which requires a long time and considerable labor and imposes a heavy burden on the users.